WO2009098403A2 - Cell for electrolysis of water with a solid electrolyte containing little or no noble metals - Google Patents

Abstract

The invention relates to a cell for the electrolysis of water comprising an essentially flat cation-exchange polymer membrane (1), two electrodes (2, 3) situated respectively to either side of the membrane (1), a catalyst place between the membrane (1) and one of the electrodes (2), characterised in that at least one of said electrodes is at least covered by a film made up of large specific surface area support comprising elements of a micrometre or nanometre scale, which in particular can be nanoobjects, nanostructures, nanotubes, nanoelements, said catalyst being adsorbed on each of said elements.

Description

 CELL FOR ELECTROLYSIS OF WATER WITH SOLID ELECTROLYTE CONTAINING LITTLE METALS

The present invention relates to an electrochemical cell with solid polymer electrolyte, its manufacturing method and a stack of several of these cells. It applies more particularly, but not exclusively, to the electrolysis of water for the production of hydrogen and oxygen, in particular for the supply of gas to fuel cells.

In general, solid polymer electrolyte cells comprise a thin ion exchange membrane (approximately 200 μm), and a metal electrode on each side, one serving as a cathode and the other anode. These electrodes consist of a collector (also called a distributor) current covered or not on the surface of a catalytic layer placed in contact with the membrane. It may be, for example, porous titanium plates that allow the gases produced by the electrolysis reaction to escape. The reactions that occur are the following: - at the anode: 2 H ₂ O → 4 H ⁺ + 4 e- + O _2, - at the cathode: 4 H ⁺ + 4e ^" → 2 H ₂

In electrolysis of water, the electrodes are connected to a DC electric generator. The anode and the cathode are supplied with pure water, that is to say in very highly demineralised water. Oxygen evolution takes place at the anode while the protons produced by the decomposition of the water pass through the membrane towards the cathode where they are reduced to hydrogen. Each proton carries with it a procession of solvating water molecules. During the electrolysis, there is thus permanent circulation of protons inside the membrane, and water transport from the anode to the cathode. This flow of water is called electro-osmotic flow. The water is discharged through the porous titanium collector together with the gaseous hydrogen.

In the state of the art, the membranes are generally made of perfluorosulphonated polymers, very chemically and electrochemically stable. These polymeric materials consist of a network of fixed anions and mobile or labile cations within this network. The NAFION ® membranes developed by the company Dupont de Nemours are an example of a membrane commonly used in this type of application. The anions are SO3 ions ^"and the cations can be of various kinds: Na ^+, K ^+, Li ⁺ For applications in electrolysis of water, mobile species are protons H ^1.".

In order to increase the energy efficiency of these cells, the metal catalysts located between the membrane and the current collector are chosen, for a given reaction, according to several factors: their electrocatalytic power, which varies according to the metal and the available exchange surface,

their chemical stability with respect to the acidic acid and the reaction, in particular the anodic side (production of oxygen),

their electrochemical stability as a function of the electrode potential, their electronic conductivity, which also varies according to the porosity of the catalytic layer,

- their cost.

The state of the art in the electrolysis of alkaline water consists of using inexpensive catalysts based on nickel. But in the case of electrochemical cells with solid polymer electrolyte (initially developed in to make fuel cells for space applications), only catalysts based on precious metals (Platinum, Iridium, Ruthenium, Gold, Rhodium or Palladium), or their oxides (such as IrO ₂ , RuO ₂ ), capable of withstanding the acidity of the polymer membranes, are used. They are therefore very expensive.

The choice of catalyst is different from the cathodic side and the anodic side:

- The best known catalyst for the release of Hydrogen is Platinum. The Platinum contents are of the order of 0.2 to 0.5 milligram of platinum per cm ² of geometric electrode area;

- On the anode side (release of O ₂ ), is usually used as the catalyst of Iridium, deposited directly on the membrane and / or on the electrode.

The invention more particularly aims to reduce to a minimum the amount of precious metal used as a catalyst compared to the state of the art, or even to remove any precious metal, at least on an electrode, in order to lower the cost water electrolysis cells with solid polymer electrolyte.

For this purpose, the invention proposes in a cell for electrolyzing water comprising a cation exchange polymer membrane, two electrodes located respectively on either side of said membrane, a first catalyst for the reduction of protons in molecular hydrogen. placed between the membrane and the cathode, characterized in that at least one of the electrodes is at least covered with a film consisting of a high surface area support composed of elements having a micrometric or nanometric size, elements on each of which is adsorbed said catalyst. The term "high surface area support" is intended to mean any support composed of elements having a micrometric size, which may consist of carbon black, or preferably of a nanometric size that may consist in a non-limiting manner of nanoobjects, nanostructures , nanotubes, nanoelements, etc.

The provisions according to the invention make it possible to reduce the charge (that is to say the quantity per unit area expressed in mg / cm 2) of "noble catalyst" of precious metal or noble metal type, while increasing catalytic surface. Thus, with an equal exchange surface, the amount of noble catalyst will be considerably reduced compared with that which would be necessary in the case of a homogeneous catalyst layer.

By way of example, the noble catalyst charge required during the implementation of the invention

• is between 0 and 0.01 mg / cm ² at the cathode, and

• is strictly greater than 0 and less than 0.2 mg / cm ² at the anode against a charge found in the state of the art of the order of 0.5 mg / cm ² of Pt at the cathode, and an Iridium filler of the order of 1 to 2 mg / cm ² at the anode.

Advantageously, said first catalyst may comprise at least one compound belonging to at least one of the following families:

• Family of heteropolyacids (HPA) stable in aqueous medium,

• Family of stable metal oximes in aqueous medium, • Platinum nanoparticles.

The invention proposes in particular the use of compounds of the family of HPA on the surface of the cathode, as long as they are stable in aqueous media, to replace the platinum commonly used in the state of the art. Since many of them are soluble in water, the invention proposes a method (described later) allowing their use in the context of a the electrolysis of water with solid polymer electrolyte and the maintenance of their electrochemical properties over long periods. For example, the invention provides the use of a tungstosilicic acid (H ₄ SiW ₁₂ O ₄₀ ) which is a simple, commercially available HPA which has a Keggin structure. The invention also proposes HPA of the same family (PW ₁₂ and PMo ₁₂ ) and more complex HPA type P ₂ Wi ₈ (saturated and substituted structure of the Dawson type).

The invention also provides HPAs based on palladium or platinum or iridium. Although having a noble metal and therefore more expensive, they have the property of adsorbing very strongly in the form of monolayers on the surface of suitable supports which reduces the amount used.

Alternatively, the invention also proposes not to completely remove the Platinum but drastically reduce the amount used by using it in the form of nanoparticles adsorbed on the high surface area support.

Different noble metal free catalysts can be used to replace platinum on the cathodes. For example, some heteropolyanion (HPA) are known to catalyze the hydrogen evolution reaction in acidic medium. HPA is a compound which results from the condensation of oxometallates around a heteromate and whose general formula is X _x M _1n O _y ^{11 "} where X is the heteroelement (for example P, As, Si) and M is the metal (for example W, Mo, V) The HPA can be arranged mainly according to two types of structures:

X = 1 and m = 12 correspond to a so-called KEGGIN structure (for example SiWi ₂ O ₄₀ ^{3 "} ) _* • x = 2 and m = 18 correspond to a so-called DAWSON structure (for example PzWi ₈ O ₆₂ ^6" ). HPA's are very stable acids. They have a high molecular weight, a high solubility in water and in organic solvents, and a large capacity of storage and transfer of electrons and protons without change of structure. They can stably modify the surface of the electrodes by simple adsorption.

The patent application FR 2 573 779 describes electrodes activated using HP A, their preparation and their application, especially as a cathode for the electrolysis of water in acidic medium. The objective pursued is the same, but it is clear from this document that the intended application for these electrodes is that of electrolysis in a liquid medium (page 5 paragraph 8) and not that of the electrolysis of water to solid polymer electrolyte. In addition, the procedure used to adsorb the HPA on the surface of the working electrode (low potential cathodic polarization), is different from that of the invention. In the case of a solid electrolyte, there is the problem of the stabilization of the HPA in the vicinity of the current collectors. Indeed, the electro-osmotic flow causes a leaching of the cathode and even if the HPA are strongly adsorbed on the surface of the collectors, in the long run, they dissolve and the efficiency of the cell is degraded. The invention overcomes this problem through a manufacturing method described below.

It is understood that the invention also relates to the use of HPA adsorbed on the surface of non-noble metal nanoparticles such as titanium.

The invention provides other compounds free of noble metals that catalyze the reduction of protons to hydrogen.

According to one embodiment of the invention, said catalyst used for the reduction of hydrogen protons may be a compound belonging to the family of stable metal oximes in an aqueous medium. Advantageously, said family of metal oximes comprises the clathrochelate complexes of formula I:

said clathrochelate complex comprising: - a metal center M of the first series of transition elements of the periodic table of elements

three glyoximate ligands around said metal center M, each of said glyoximate ligands being substituted with a radical R ¹ , R ² , R ³ , R ⁴ , R ⁵ , or R ⁶ , each radical R ¹ , R ² , R ³ , R ^4; , R ⁵ , or R ⁶ being independently an alkyl or phenyl group, substituted or unsubstituted.

an atom A belonging to the elements of group 13, the said atom being linked to the three glyoxime ligands,

a radical X, said radical X being a halogenide such as in particular fluorine, or an alkyl, phenyl or phenyl group functionalized with a radical Y, Y being a radical chosen from the group consisting of NO2,

F ₅ N 2 +, COOH ₅ COOEt, N 3, CHO.

According to a particular embodiment, said metal center M consists of a transition metal such as: Co, Fe or Ni. According to another particular embodiment, said atom A belonging to the elements of group 13 consists of B or Al, or elements of the same chemical family or similar properties ... According to one particular embodiment, the invention relates to the use of stable metal oximes in an aqueous medium, said aqueous stable oximes in an aqueous medium being preferentially:

Cobalt (III) dimethylglyoxime Co (dmgBF ₂ ) ²⁺ , or cobalt (III) diphenylglyoxime Co (dρgBF ₂ ) ²⁺

The highly oxidizing conditions prevailing at the anodes of electrolysers make it difficult to use these precious metal-free catalysts for long periods of time to replace Iridium. The invention proposes to use HPAs comprising precious metals, which make it possible to reduce the quantity of precious metal used, such as:

• A HPA based on platinum, e.g. shorthand α ₂ - K ₈ PtP ₂ W ₁₇ O ₆₁ • A HPA based on palladium, e.g. abbreviated formula O ₂ -K ₈ PoP ₂ W ₁₇ O ₆ I ,

An iridium-based HPA, for example of the abbreviated formula α2-K8IrP2W17O61.

The invention also proposes to use:

• aqueous stable Ruthenium-based molecular compounds such as: cis, cis - [(bpy) ₂ (H ₂ O) Ru ^m ORu ^m (OH ₂ ) (bpy) ₂ ] ⁴⁺ cis, cis - [( phen) ₂ (H ₂ O) Ru ^πi ORu ^m (OH ₂ ) (phen) ₂ ] ⁴⁺ • Manganese-based molecular compounds such as: tMn ₂ O ₂ (bipy) 4] (ClO ₄ ) 3 [Mn ₂ O ₂ (phen) ₄ ] (ClO ₄ ) ₃

The invention also proposes using nanoparticles of Iridium and / or Ruthenium or their oxides, which also make it possible to reduce the quantity of precious metal used. The anodes and cathodes can be obtained:

Or by depositing the catalyst directly on the surface of the current collector, for example made of porous titanium,

Or by depositing on the current collector a support with a large specific surface on which the catalyst will have been previously adsorbed.

For example, on the cathodic side, the invention proposes as support material a carbon powder, such as Vulcan XC72 from Cabot Co (surface area 250 m ² / g) or a carbon nanotube powder.

In order to reduce the precious metal contents, the invention proposes as a material a support with a large specific surface area of the nanoparticles of titanium oxide below stoichiometric of general formula TiO ₂ . _x . While titanium oxide is a semiconductor, the fact of partially reducing it, for example by hydrogen, makes it an electronic conductor. Moreover, it can be obtained in the form of a nanometric powder and is relatively cheap. The invention proposes, for example, adsorbing iridium or ruthenium nanoparticles (or their oxides) on TiO ₂ . _x .

The invention also proposes a method for manufacturing a solid electrolyte electrochemical cell comprising a polymer membrane, an anode and a cathode and at least one catalyst between the membrane and the cathode.

The current collectors, for example porous titanium, are previously stripped of their surface oxides, degreased and dried. The catalyst is then solubilized in a solvent, for example isopropanol.

The mixture is sprayed by means of an air-blast sprayer on an electrode face maintained at a temperature of about 100 ^° C. in order to evaporation of the solvent and to prevent the catalyst from settling inside the porous titanium collector.

A polymer film, for example of Nafion, is then sprayed by the same method on the face of the electrode which has received the catalyst and the electrode is dried at a temperature of about 100 ^° C. in order to cause evaporation. solvent. It is important that the thickness of the polymer film is not too great to obtain a good electrochemical response. To control the thickness of the film, the commercial solutions should be diluted in a solvent such as isopropanol by a factor of 10 to 1000. The films giving the best results have a thickness of about 100 microns.

The electrode thus obtained is then placed in an electrochemical cell with three electrodes for activation. It can be activated by cyclic voltammetry between 0 and -750 mV / ECS, under evolution of hydrogen in an acid solution of concentration 10 ^-2 M to 1 M, with a scanning speed of about 5 mV / s. a few hours, the activity is maximum.

The cathode is then pressed against a perfluorosulfonated polymer membrane, for example Nafion or Hyflon, in a suitable Titanium support. Hot water is circulated in the cell, approximately 95 ^° C., for one hour. A low current, less than 100 mA / cm ² , is then passed for about 2 hours.

Finally, the preparation is terminated by subjecting the cell to a constant voltage of about 2 volts for about 12 hours. At the end, the electrode is secured to the membrane by interleaving the polymer chains of the film in the membrane. Good adhesion produces the best performance in electrolysis. The process described above is applicable for both the cathode and the anode.

Alternatively, the invention proposes that said support having a large specific surface area consists in particular of carbon powder for the cathode or TiO 2-x for the anode, said high surface area support being dispersed in a catalyst solution (in proportions 1-1% by volume) using an ultrasonic tank to ensure good dispersion, to spray the preparation on the current collector, and then to deposit a protective polymer film.

Alternatively, the invention proposes to spray on the current collector, in a single step, a mixture of substrate + catalyst + polymer solution.

HPAs also exhibit activity against the oxidation of hydrogen to protons. They can therefore be used in the anodes of solid electrolyte fuel cells. The platinum nanoparticles dispersed on the high surface area support such as carbon have a high activity with respect to the reduction of oxygen in water. The innovative electrochemical cell described above can therefore be used in fuel cell operation, provided that the current collectors (made of porous titanium) are replaced by hydrophobic gas diffusion electrodes, such as those used in the state. art.

Since the innovative cell can operate in electrolyser mode and in fuel cell mode, it can also be used to operate in reversible mode, that is to say sometimes in electrolyser mode, sometimes in fuel cell mode. The performance of such reversible systems is optimal when the catalysts are specialized by type of redox process rather than by type of gas. Thus, a compartment is used for reduction processes (reduction of hydrogen protons in electrolyser mode and reduction of oxygen in fuel cell mode), and another to oxidation processes (oxidation of water to oxygen in electrolyser mode and oxidation of hydrogen to protons in fuel cell mode). In this case, it is necessary to use catalyst combinations on each of the two electrodes.

A particular mode of preparation of the membrane and the electrodes according to the invention is provided below by way of non-limiting example.

STEP 1: Preparation of the membrane

A membrane of Nafion ^® (Pont de Nemours) 140mm thick is placed in an aqueous solution (400 mL, distilled water) HNO3 (10% W) and then heated at 100 ⁰ C for 30 min (including rise in T ⁰ C). It is then rinsed in hot distilled water (400 mL, 10 min) and then at ambient temperature baths. The rinse ends with multiple quick washings with water.

STEP 2: Preparation of the electrodes

Necessary material of a particular embodiment according to the invention:

• The anode and cathode consist of porous Ti disks with the following characteristics: 7cm in area, 3cm in diameter, 0.85mm in thickness, and a porosity of 25-28%. The experimenter shall take care to avoid any contact of the faces with a potentially contaminating source, (and in particular to avoid contact with the fingers, the heating plate or the balance, to use clean machine paper as a support and to always grasp an electrode with pliers on the edge).

Catalysts: the anodic catalyst used is Iridium; the cathode catalyst is a colbalt-oxime complex. The reference cathode catalyst is platinum adsorbed on activated carbon (Pt / c). Nafion solution: 6.5% Nafion ^® (DuPont de Nemours) in isopropanol (iPrOH).

Final amount of catalyst per unit area (catalyst load expressed in mg / cm 2): the final load is 2.5 mg / cm 2 of catalyst knowing that Nafion ^® must constitute 5% by weight of the catalytic layer. For a surface of 7 cm 2: add 17.5 mg of catalyst to 0.9 mg of Nafion solution at 6.5% to obtain a total weight of 18.4 mg.

• Vaporization of the catalyst: The catalyst is deposited on the surface of the electrode by vaporization under pressure using a compressed air gun.

Experimental protocol :

Weighing of bare Ti disks

The weighing of the bare Ti discs is carried out by heating a plate at 100 ^° C. on which the Ti discs are deposited in order to evaporate any residual solvent (water in particular). When the weighing remains constant during several successive weighings, the mass of the discs is noted.

Weighing catalysts and Nafion ^® and preparing the spray solution

• For a reference cathode electrode: twice as much platinum adsorbed on activated charcoal (Pt / c) or three times more iridium than catalyst and 6.5% Nafion solution will be required due to loss of material significant during the vaporization. The ratio of the mass of catalyst in relation to that of the Nafion solution 6.5% is as follows: m _C Aτ / Nina _f io _n ⁼ 1.235, wherein m _C Aτ is the mass of catalyst, and mNafion is the mass of the Nafion solution at 6.5%. For a cathode electrode comprising a cobalt oxime complex according to the invention: mix 50% by weight of carbon black and 50% by weight of cobalt oxime complex.

• The necessary 6.5% Nafion solution is pre-weighed. In the case of the reference cathode electrode the weighing is 28 to 43 mg [i.e. 2σu3xl7.5 / 1.235]. The amount of 6.5% Nafion solution thus obtained is diluted in a little isopropanol. • The corresponding amount of catalyst is then weighed by observing certain precautions, in particular for platinum adsorbed on activated charcoal (Pt / c), it is necessary just after the weighing to pour a few drops of water to the powder to avoid that it does not react to the addition of iPrOH. "The Nation solution is poured into the pillbox of the catalyst, then TiPrOH is added if necessary. The catalyst + Nafion mixture thus obtained is subjected to ultrasound (here ultrasonic probe) to disperse until a homogeneous suspension.

In order to verify that said homogeneous suspension is obtained, the following test is carried out: the contents of the pill pillar are poured into another receptacle so that no solid deposit remains at the bottom or very little. Placing the catalytic layer on the electrode

• The disks are placed again on the heating plate at 100 ^° C. Thus, the maintenance of the disks at this temperature allows the quasi-immediate evaporation of the solvent when the solution is vaporized on the electrode (this in order to strongly limit the penetration within the porous Ti).

• Half or one third of the solution of the catalyst + Nafion mixture is poured into the tank of the air pistol to be sprayed over the entire disc as homogeneously. as possible (concentric movement ~ 10cm from the medium flow plate). Between each spray, let it evaporate a few seconds.

• After vaporization of this first part of the initial solution the sample is weighed.

If the catalyst load is sufficient, the vaporization is complete. In the opposite case (probable), the rest of the solution with re-diluted in PiPrOH is sonicated, and again half poured into the tank of the air pistol

• compressed, to be a second time vaporized, etc. This operation is repeated until the desired final catalyst load is reached.

Embodiments of the invention will be described below, by way of non-limiting examples, with reference to the accompanying drawings in which: FIG. 1 is a diagrammatic sectional view of a membrane hydrolysis cell,

Figures 2 and 3 show Voltage x current density curves obtained with different catalysts.

In Figure 1 there is a polymer membrane 1, for example Nation or Hyflon, a cathode 2 and anode 3 applied against the membrane I ₅ porous metal to allow the release of gases H2 and 02, for example porous titanium. The cell is powered by a DC source 4. The cell is supplied with purified water at the cathode 2 and the anode 3.

Between the cathode 2 (respectively the anode 3) and the membrane 1 there is a layer of a first catalyst 5b (respectively second catalyst 5a). These catalysts may have been deposited directly on the cathode or on the anode, but they have preferably been adsorbed beforehand on a material with a large specific surface area, such as tin nanoparticles on the anode side. In the state of the art, the first catalyst 5b consists of platinum particles and the second catalyst 5a of Iridium particles.

Figure 2 illustrates the catalytic effect of Platinum at the cathode and Iridium at the anode. The laws of thermodynamics indicate that the minimum voltage to be applied to a water electrolysis cell operating at 25 ° C is 1.23 V, regardless of the current density. Because of the resistances induced in particular by the membrane and the electrodes, on the one hand the voltage to be applied for the start of the reaction is slightly higher (1.4 V minimum), on the other hand it is necessary to increase the voltage applied if we want to increase the current density. Nevertheless the cell will be all the more efficient that will obtain a higher current density for a given voltage. The curves of FIG. 2 are obtained with a Nafion membrane 115 and titanium electrodes and with the following catalysts: curve 1: deposit of carbon at the cathode and deposition of Iridium at the anode (the carbon shows a slight catalyst effect),

curve 2: cobalt-oxime Co (dpgBF ₂ ) ²⁺ adsorbed on carbon at the cathode and Iridium at the anode, curve 3: particles of platinum at the cathode and iridium at the anode.

Curve 1 is obtained without catalyst at the cathode but with Iridium at the anode. It can be seen that the current density increases very slowly with the voltage applied to the cell. Curve 3 illustrates the state of the art with precious metal catalysts at the cathode and at the anode. Curve 2 illustrates the catalyst effect of a cobalt oxime in a PEM membrane electrolysis cell. Thus, a current density of 250 mA / cm 2) requires a voltage of about 2.1 V without catalyst (curve 1), 1.65 V with an HPA catalyst (curve 2) and 1.56 V with platinum catalysts and Iridium. Such high current densities are not obtained with a cobalt oxime catalyst but its cost is much lower than the Platinum it replaces.

FIG. 3 illustrates the performances obtained with various catalysts and a Nafion 117. membrane. Curve 1 is the result of the state of the art: catalyst platinum at the cathode and iridium at the anode. Curve 3 is a result obtained with Platinum at both electrodes: Platinum is a less good anodic catalyst than Iridium. Curve 2 illustrates the catalytic effect of HPA: at the same temperature of 80 ^° C., the results are intermediate between those of curves 1 and 3. It should be noted that these results were obtained without support material with a high specific surface area. such as carbon black at the cathode, so it's about minimum performance.

Curves 4 and 5 illustrate the effect of temperature: the cell's performance drops with the temperature falls from 74 to 50 ^° C. The results obtained with the different HPA are very close.

Claims

claims

1. Cell for the electrolysis of water comprising a substantially planar polymeric cation exchange membrane (1), two electrodes (2, 3) located respectively on either side of said membrane (1), a catalyst placed between the membrane (1) and one of the electrodes (2), characterized in that at least one of the electrodes is at least covered with a film consisting of a high surface area support composed of elements having a micrometric size or nanoscale which can consist in particular of nanoobjects, nanostructures, nanotubes, nanoelements, elements on each of which is adsorbed said catalyst.

2. cell for the electrolysis of water according to claim 1, characterized in that said catalyst adsorbed on said elements having a micrometer or nanometer size is the first and / or second catalyst (5a, 5b).

3. Cell for the electrolysis of water according to one of claims 1 or 2, characterized in that said first catalyst (5b) comprises at least one compound belonging to at least one of the following families:

• Family of heteropolyacids (HPA) stable in aqueous medium,

• Family of stable metal oximes in an aqueous medium,

• Platinum nanoparticles.

4. Cell for the electrolysis of water according to claim 3, characterized in that said first catalyst (5b) of the family of HPA comprises at least one compound selected from the following list:

• An HPA of the SiWi ₂ family,

• An HPA of the PWi ₂ family, • An HPA of the PMOi ₂ family,

• An HPA of the P ₂ Wi _{8 family} , • Platinum based HPA,

• Palladium-based HPA,

• An HPA based on Iridium.

5. cell for the electrolysis of water according to claim 3, characterized in that said first catalyst (5b) of the family of metal oximes comprises a clathrochelate complex of formula I:

said clathrochelate complex comprising: - a metal center M of the first series of transition elements of the periodic table of elements

three glyoximate ligands around said metal center M, each of said glyoximate ligands being substituted by a radical R1, R2, R3, R4, R5, or R6, each radical R1, R2, R3, R4, R5, or R6 being independently an alkyl group or phenyl.

an atom A belonging to the elements of group 13, the said atom being linked to the three glyoxime ligands,

a radical X, said radical X being a halogenide such as in particular fluorine, or an alkyl, phenyl or phenyl group functionalized with a radical Y, Y being a radical chosen from the group consisting of NO2,

F, N 2 +, COOH ₅ COOEt ₅ N ₃ CHO.

Cell for electrolysis of water according to claim 5, characterized in that said metal center M is made of a transition metal such as Co, Fe or Ni.

7. Cell for the electrolysis of water according to one of claims 5 or 6, characterized in that said atom A belonging to the elements of the group

13 consists of B or Al, or elements of the same chemical family or similar properties

8. cell for the electrolysis of water according to claim 5, characterized in that said first catalyst (5b) of the family of metal oximes comprises at least one compound selected from the group consisting of:

- Cobalt dimethyl glyoxime of abbreviated formula Co (dmgBF2) ²⁺ , or

- Cobalt diphenyl glyoxime of abbreviated formula Co (dpgBF2) ^{? +} .

9. Cell for the electrolysis of water according to one of claims 1 to 8, characterized in that said second catalyst (5a) comprises at least one compound selected from the following list:

• Platinum-based HPA, • Palladium-based HPA,

• An HPA based on Iridium,

• A stable ruthenium molecular compound in an aqueous medium,

• nanoparticles of Ruthenium oxide,

• A molecular compound based on Manganese.

10. cell for the electrolysis of water according to claim 9, characterized in that said support with a large surface area on the cathode side (2) is a carbon powder or carbon nanotubes.

11. Cell for the electrolysis of water according to claim 9, characterized in that said high anode-type surface-area support (3) is a compound selected from the following list:

• Titanium oxide nanoparticles under stoichiometric conditions,

• Nanoparticles of tin oxide.

12. Electrolyser characterized in that it comprises a stack of cells for the electrolysis of water according to any one of the preceding claims.

13. Process for the preparation of a cell for the electrolysis of water comprising a substantially planar polymeric cation exchange membrane (1), two electrodes (2, 3) located respectively on either side of said membrane ( 1), comprising at least a first catalyst (5b) for proton reduction in molecular hydrogen placed between the membrane (1) and the cathode (2), said first catalyst (5b) comprising at least one compound belonging to at least one one of the following families:

• Family of heteropolyacids (HPA) stable in aqueous medium,

• Family of stable metal oximes in an aqueous medium,

Platinum nanoparticles, said process comprising the steps of:

• Solubilize the catalyst in a solvent,

• Spray the mixture on an electrode face (2, 3) by heating said electrode,

• Spray a polymer film on said face of the electrode (2, 3) having received the catalyst by heating said electrode.

The method of claim 13 further comprising the step of further dispersing the high surface area carrier in the solution containing said catalyst, prior to spraying, so as to adsorb said catalyst to the surface of said high surface area carrier.

15. The method of claim 13 or 14 wherein the polymer is further solubilized in the solution containing said catalyst and then sprayed in one operation said solution on an electrode face by heating said electrode.

16. Method according to one of claims 13 to 14 further comprising a subsequent step of activating said electrode by cyclic voltammetry.

17. Method according to one of claims 13 to 16 further comprising the following subsequent steps:

• Press the face of the electrode (2, 3) which has received the catalyst and the polymer film against the membrane (1) of said cell,

• Circulate hot water in the cell,

• Pass a weak current in said cell, • Submit said cell to a DC voltage.

18. Use in a fuel cell of a cell comprising a substantially planar polymeric cation exchange membrane (1), two electrodes (2, 3) located respectively on either side of said membrane (1), a first catalyst (5b) of the proton reduction in molecular hydrogen placed between the membrane (1) and the cathode (2), said first catalyst (5b) comprising at least one compound belonging to at least one of the following families:

• Family of heteropolyacids (HPA) stable in aqueous medium, • Family of stable metal oximes in aqueous medium,

• Platinum nanoparticles.

19. Use in a reversible electrolyser-cell stack of a cell comprising a substantially planar polymeric cation exchange membrane (1), two electrodes (2, 3) located respectively on either side of said membrane (1), a first catalyst (5b) for the reduction of protons in molecular hydrogen placed between the membrane (1) and the cathode (2), said first catalyst (5b) comprising at least one compound belonging to at least one of the following families:

• Family of heteropolyacids (HPA) stable in aqueous medium, • Family of stable metal oximes in aqueous medium,

• Platinum nanoparticles.